The exemplary embodiments described herein relate to fracturing operations of subterranean formations.
Subterranean formations are often stimulated by hydraulic fracturing operations to enhance the volume of fluid produced from the formation in later production operations. In traditional hydraulic fracturing operations, a fracturing fluid, which may also function simultaneously or subsequently as a carrier fluid, is pumped into a portion of a subterranean formation at a rate and pressure sufficient to create or extend at least one fracture therein. Typically, particulate solids, often referred to as proppant particles, are suspended in a portion of the fracturing fluid or subsequently introduced proppant slurry. The proppant particles fill at least a portion of the fractures to form a proppant pack and serve to prevent the fractures from fully closing once the hydraulic pressure is removed. By keeping the fractures from fully closing, conductive paths are formed through which fluids produced from the formation may flow.
The degree of success of a subsequent production operation depends, at least in part, upon on the design of the fracturing operation and its relative optimization vis-à-vis the particular formation in which it will be placed. Designing the right fracturing operation for a given application often involves modeling many interrelated parameters including materials (e.g., fracturing fluids, proppants, etc.), tools (e.g., zonal isolation devices, etc.), pumping schedules, treatment pressures, fluid rates, fracture mechanics, and the parameters relating to the well bore and the surrounding subterranean formation (e.g., rock type, deviation of the well bore, depth of the zone in the formation to be fractured, etc.) Predicting the outcome and results of a fracturing operation is important to not only maximize production levels for hydrocarbons, but also protect water tables and other surrounding concerns.
To design fracturing methods optimized for the specific interrelated parameters associated with a given job or project, oftentimes researchers create lab scale models mimicking the subterranean formation, rock type, rock mechanics, and other parameters affecting fracturing of subterranean, which are referred to as synthetic test beds (STBs). Using these STBs, researchers can test theories relating to the interrelated parameters involved in the fracturing operation to design a particular fracturing job.
Standard STBs usually consist of homogenous plastic blocks, e.g., polymethylmethacrylate blocks, like that illustrated in FIG. 1. The STB is placed in a test rig and then fractured using conditions and fluids of interest. Although the clearness of the plastic in the STB enables the observer to observe the fracturing effect of an injected modeled fluid, the monolithic nature and homogeneity of the STBs composition is not representative of actual sedimentary rock. Sedimentary rock is a layered composite structure (e.g., bedding planes), each layer potentially having different characteristics (e.g., rock mechanical properties) that may affect a fracturing operation. Thus, these homogenous plastic STBs are not able to model a fracturing operation sufficiently to optimize fracturing operations. Consequently, observers cannot gain an adequate understanding of the relative effect of changes in the interrelated parameters (e.g., stress interference, rate, viscosity, process order, etc.) that affect the modeled fracturing operations. Additionally, observers are unable to accurately test or create optimized hypotheses from which more predictable fracturing operations result, which is important because of the extra scrutiny placed on fracturing operations.